Asphalt bituminous bonding composition and process of preparation



Patented Dec. 19, 1950 UNITED ASPHALT IBETUMKNUUS BGNDING COMPO- SITIQN AND PROCESS OF PREPARATEON" Lloyd- .E. Mitchell, Berkeley, and Harry .l. Summer,

Lafayette, @aliil, assignors to Shell. Development Company, San Francisco, case, a corporation. of Deiaware No Drawing. Appiication August 14, 1948, Serial No. 44,404

6 Claims. 1

This invention relates to improvements inbituminous compositionssuch as asphalt, asphalt cut-back and asphalt emulsions. More particularly, it i concerned with improving the bonding characteristics of such substances and with a method for carrying out the improvement.

It has been determined by numerous investigators that bituminous substances such as asphalt do not normally adhere to surfaces such as mineral aggregates, metals and other objects in the presence of water. It has been established that water will more or less readily displace asphalt films therefrom. The use of various additives to overcome this adverse characteristic has been widely recognized. Three main types Of additives have been employed for this purpose. These include high molecular weight acids, soap and amines. Various combinations of these have been used, and water-soluble materials such as metallic salts, have been used for priming the surface before coating with a bituminous material.

The configuration and characteristics of these additives vary widely, as would be expected. Some are applicable to basic rocks, such as limestone; others to acid rocks, such as granite, while certain species may be employed on any type of surface or with asphalts from a variety of sources.

One of the shortcoming to which most of these adhesion agents are subject is the tendency for the effect of the agent to decrease if the asphalt in which it is contained is subjected to aging or heating. This is a serious shortcoming from a practical standpoint, since it is advantageous to add the agent to the asphalt, cut-backs and road oils prior to shipment to road-laying or building sites. During such shipments, the asphalt, cut-backs and road oils are maintained for extensive periods at elevated temperature. This period of heatin may continue for as long as a week or more; hence, any additive employed under such conditions should possess the ability to maintain its adhesion improving quality under these conditions.

Many amines are satisfactory for improving the adhesion characteristics of bituminous compositions as long as stability to heating is not a factor. However, it has been found that longchain amines, such as octadecylamine, are unstable under heating conditions such as those described above. Likewise, cyclic amines, such as heptadecylimidazoline, are unstable under such conditions.

It is an object of the present invention to provide bituminous compositions having improved bonding characteristics. It is another object of this invention to provide a process for the preparation of such compositions. Other objects will become apparent during the following discussion.

Now, in accordance with the present invention', ithas been found that oleophilie pyrimidines having a particular coni'i guration possess a unique property which makes their-use as antistripping agents in bituminous substances unexpectedly advantageous. ered that the adhesion effect of certain'su-bstituted pyrimidines in asphalt actually improves when the asphalt composition containing them is heated.

Still in accordance with this invention, it hasbeenfound that because of this unaccountable phenomenon, asphalt compositions containing the class of substituted pyrimidines described hereinafter are superior to asphalts containingthe various amine-type adhesion agents, since the latter become poorer in adhesion characteristics when heat treated.

Bituminous substances which may be improved according to thepresent invention include especially pyrogerous residues, such as asphalts and pitches, as well asnatural asphalts and tars, such as coal tar. Asphalts employed'for the preparation of roads, airports and similar surfaces are especially suitable for the treatment to be described.

The substituted pyrimidines have the general structure:

Wherein each R; is a hydrogen atom or an alkyl' group and at least one B is an alkyl grouphaving at least 10 carbon atoms.

Preferably, R1 is the long-chain alkyl group having at least 10 carbon atoms. Typical groups include the decyl, dodecyLtetradecyl, cetyl, ceryl and carnaubyl radicals. Another preferred structure includes those species wherein R2, R3 and R4 are short-chain alkyl radicals having 1-5 carbon atoms. These include both straightchain and branched-chain radicals, such as methyl, ethyl, amyl, etc. The species which is especially preferred is 2 heptadecyl 4,6,6- trimeth-yl-3,4,5;S-tetrahydropyrimidine.

Substituted pyrimidines having the above preferred configuration may be prepared by processes already known. An especially suitable process comprises the reaction of a long-chain fatty acid with a 1,3-diamine.

Equimolecular quantities. of thelong-chain fatty acid andthe substituted 1,3-diamineare heated in a suitable. solvent (eg xylene) inlthe presence of an-acid catalyst, with. the. azeotropic. removal of water as itis formed- .As the reaction proceedsand the. rate of water formation decreases, the solvent is removed. and the kettle It has been d-iscov temperature increased to l'75-200 C. When the theoretical amount of water has been collected, the reaction mixture is neutralized with calcium carbonate, and the product recovered by distillation. An actual working example is the reaction of stearic acid with Z-methyl-ZA-pentanediamine:

A solution consisting of one mole of stearic acid, one mole of 2-methy1-2,4-pentanediamine, 0.5 g. of concentrated sulfuric acid and about 200 ml. of xylene was refluxed in a water-by-distillation still for a total of 116 hours at l75-l95 C. after 0.5 mole of water and most of the xylene had been removed. During this time 1.5 moles of water were removed. The reaction mixture was then refluxed for two hours with 20 g. of calcium carbonate, topped, and the residue distilled through a short column at 2 mm. The 2- heptadecyl 4,6,6 -trimethyl-3,4 5,6-tetrahydropyrimidine cut was obtained at 184-200 C/2 mm.

Other species which may be employed in the subject compositions include 2-octadecyl-4,6,6- triethyl-3,4,5,6-tetrahydropyrimidine; 2-dodecyl- 6,6-dipropyl-3,4,5,6-tetrahydropyrimidine; 2-carnaubyl 4,6-diamyl-3,4,5,S-tetrahydropyrimid-ne; 2-heptadecyl-4,5,6,6-tetramethyl-3,4,5,6-tetrahydropyrimidine.

Depending upon the specific pyrimidine, the source of the asphalt and the type of surface to be coated, the amount of the additive to be employed may vary from about 0.1 to by weight of the asphalt. This may be added in unmodified condition or in the form of a solution to the melted asphalt, or may be sprayed or otherwise deposited as a primin coat on the aggregate or other surface as an emulsion or aqueous salt solution or as a solvent.

An unexpected feature distinguishing the subject pyrimidines from other amine-type additives comprises the response which the pyrimidines show to the effect of heat after they have been incorporated in an asphalt. This effect is demonstrated by the examples which follow. It will be noted in Examples 1, 2 and 3 that a heat treatment of one week at 120 C. increased the adhesion characteristics of the pyrimidine employed in many instances. This response to heating is in direct contrast to that noted in Examples 4 and 5, wherein other typical amines were heated after their addition to various asphalts. It has been found that this increase in bonding characteristics is exhibited by asphalt compositions containing the subject pyrimidines when they have been heated for periods longer than about one hour within the temperature range 2l0325 C.

A convenient means of effecting this heat treatment comprises adding the subject pyrimidines to the asphalt blend and conveying the asphalt to the site where it is to be used in heated tank cars. The examples which follow illustrate the process and products of the present invention and difierentiate the results obtained from those which occur when other amines are employed.

EXAMPLE 1 The anti-stripping effect of pyrimidines in various asphalts was tested as follows, using a. soda rhyolite aggregate:

The A-inch to /;-inch crushed, clean aggregate, wet with 2% by weight of water, was mixed with 6% by weight of a medium curing cut-back grade MC-2 asphalt. After curing for one hour at ambient room temperatures, the coated aggregate was covered with distilled water for twenty hours at room temperature, after which tained. The additive employed was Z-heptadecyl- 4,6,6-trimethyl-3, l,5,6 -tetrahydropyrimidine.

Table I Cencentra Per Cent of tion of Aggregate Coated Source of Asphalt Cent of Not Heat Heat Asphalt Treated Treated San Joaquin Valley None 5 5 Do 0. 5 20 85 D0 1.0 100 08 Texas Guhl None 5 5 0.5 93 100 1.0 100 100 None l0 10 0.5 90 100 l. 0 100 100 None 10 5 0.5 60 05 1. 0 95 100 EXAMPLE 2 A set of tests parallel to those described in Example 1 were run but using a granite aggregate. The data obtained are given in Table II, below:

Table II Concentra' Per Cent of tion pl Aggregate Coated Source of Asphalt Cent of Not Heat Heat Asphalt Treated Treated San Joaquin Valley None 5 5 None 5 5 None 5 10 None 5 10 EXAMPLE 3 The tests described in Example 1 were repeated, using a Meramec gravel as the aggregate, with the following results:

Table III Concentm Per cent of Aggregate tion of Ad- Coated Source of Asphalt dither, Wt. Per ent of Not Heat Heat Asphalt Treated Treated San Joaquin Valley None 5 5 Do l 0. 5 50 Do 1.0 50 75 Texas Gulf None 10 5 0.5 1.0 80 00 N one 5 5 0.5 80 Do... 1.0 80 90 Mid-Continent None 5 5 Do 1.0 80 90 2) EXAMPLE 4 Concentration of Additive, Per Cent by Wt. of Asphalt Source of Asphalt Heat Treated Not Heat Treated San Joaquin Valley EXAMPLE 5 For comparison with the data obtained in Example l with the pyrimidine additive, the tests described therein were repeated, using heptadecylimidazoline as the agent, a soda rhyolite aggregate being coated.

Table V Per cent of Aggregate Qoncentra- Coated tlon of Additive, Per Cent by Wt.

of Asphalt Source of Asphalt Not Heat Treated Heat Treated We claim as our invention: 1. A bituminous composition comprising an Per cent of Aggregate Coated asphalt and (MO-5% by Weight of a substituted 45 pyrimidine having the general formula wherein each each R is a substituent of the group consisting of the hydrogen atom and alkyl substituents, at least one of which has at least 10 carbon atoms.

2. A composition according to claim 1 wherein the R radical indicated as R1 is an alkyl group having more than 10 carbon atoms.

3. A composition according to claim 2 wherein the R radicals indicated as R2, R3 and R4 are alkyl groups having 1-5 carbon atoms.

4. A composition according to claim 3 wherein the pyrimidine is 2-heptadecyl-4,6,6-trimethyl- 3,4,5,6-tetrahydropyrimidine..

5. A bituminous composition comprising an asphalt and 0.1-5% by weight of an alkylated pyrimidine bearing at least one alkyl group having at least 10 carbon atoms.

6. A bituminous composition comprising an asphalt and 0.15% by weight of 2,4,6,6-tetra-alkyl- 3,4,5,6-tetrahydropyrimidine wherein the alkyl radicals in the 2 and 4 positions have 1 to 5 carbon atoms and the alkyl radical in the 6 position has at least 10 carbon atoms.

LLOYD J. MITCHELL. HARRY J. SOMMER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,191,295 Dohse et a1. Feb. 20, 1940 2,314,111 Tucker et a1. Mar. 16, 1943 2,370,286 Anderson Feb. 27, 1945 FOREIGN PATENTS Number Country Date 847,829 France July 10, 1939 

1. A BITUMINOUS COMPOSITION COMPRISING AN ASPHALT AND 0.10-5% BY WEIGHT OF A SUBSTITUTED PYRIMIDINE HAVING THE GENERAL FORMULA 